Singlet and triplet excited state data on two new core-modified expanded porphyrins and their protonated derivatives are reported. Absorption spectral studies indicate a gradual red shift of the absorption bands upon sulfur substitution into the core. The singlet lifetimes for expanded S 3-sapphyrin and S 4-rubyrin decrease steadily relative to STPPH and S 2 TPP owing to a higher rate of intersystem crossing. Furthermore, the protonated derivatives of S 3-sapphyrin and S 4-rubyrin encapsulate fluoride ions into their cavities with binding constants of 807 and 48 M−1 respectively. However, the triplet lifetime for S 3-sapphyrin is longer (58.80 μs) than for normal thiaporphyrins (STPPH, 37.45 μs; S 2 TPP , 20.96 μs), suggesting that it could be very well suited for photosensitizing triplet oxygen.

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